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CaS:Eu2+,Ce3+ are widely used in various fields, which is due to their excellent luminescent properties. However, the traditional high-temperature solid state synthesis of CaS has the disadvantage of large particle size and easy agglomeration. Also, the CaS-based material is unstable and decomposes easily in humid air. In the present study, CaS:Eu2+, Ce3+(here denoted as CaS:EuCe) phosphors with a uniform particle size, good dispersion, and small particle size (Dv50 = 13.46 μm, abbreviated as D50) have been obtained using a novel coprecipitation-mesophase decomposition (CMD) method. In addition, the inorganic-organic bilayer modification technology has been used to form core-shell structured CaS:EuCe@CaZnOS@Si69 phosphors, which could resist acidic/basic solutions and moist air. Its surface property changed from hydrophilicity (water contact angle 37.28°) to hydrophobicity (water contact angle 112.23°). Finally, the optimized phosphor was used to prepare luminescent film laminated glass, which showed the potential for use in plant growth. The reaction process of the CaS phosphor, as prepared by the CMD method, and the mechanism of the bilayer surface modification, have here been discussed in detail. We believe that the here-developed synthesis method provides a new strategy for the preparation of high-performance chalcogenide phosphors. [ABSTRACT FROM AUTHOR]

Phosphor‐converted materials play a very important role in modern facility agriculture, both in converting the excess green light and low‐efficiency ultraviolet (UV) into the red and blue light that is beneficial for the plant growth, and in slowing down the aging of polymer films. In this work, UVC absorption of Zn0.5Mg0.5Al2O4 (ZMAO):Cr3+ was significantly improved by co‐doping Tb3+. The energy transfer (ET) from Tb3+ to Cr3+ occurred through a dipole–quadrupole interaction mechanism and the ET efficiency (ηET) from was up to 99.90% in the ZMAO:0.5%Tb3+, 3.0%Cr3+ phosphor, which improved the match between the phosphor emission and absorption spectra of the phytochrome PFR. Finally, light‐conversion polymeric film is achieved by coating ZMAO:Tb3+, Cr3+ phosphor. This study provides a strategy to efficiently covert the UVC and green components of the sunlight to far‐red light promoting the plant growth in horticulture and extending the service life of polymer film. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report preparation, characterization and luminescent mechanism of a phosphor Sr1.5Ca0.5SiO4:Eu3+,Tb3+,Eu2+ (SCS:ETE) for white-light emitting diode (W-LED)-based near-UV chip. Co-doped rare earth cations Eu3+, Tb3+ and Eu2+ as aggregated luminescent centers within the orthosilicate host in a controlled manner resulted in the white-light phosphors with tunable emission properties. Under the excitation of near-UV light (394nm), the emission spectra of these phosphors exhibited three emission bands: one broad band in the blue area, a second band with sharp lines peaked in green (about 548nm) and the third band in the orange–red region (588–720nm). These bands originated from Eu2+ 5d→4f, Tb3+ 5D4→7F J and Eu3+ 5D0→7F J transitions, respectively, with comparable intensities, which in return resulted in white light emission. With anincrease of Tb3+ content, both broad Eu2+ emission and sharp Eu3+ emission increase. The former may be understood by the reduction mechanism due to the charge transfer process from Eu3+ to Tb3+, whereas the latter is attributed to the energy transfer process from Eu2+ to Tb3+. Tunable white-light emission resulted from the system of SCS:ETE as a result of the competition between these two processes when the Tb3+ concentration varies. It was found that the nominal composition Sr1.5Ca0.5SiO4:1.0%Eu3+, 0.07%Tb3+ is the optimal composition for single-phased white-light phosphor. The CIE chromaticity calculation demonstrated its potential as white LED-based near-UV chip. [Copyright &y& Elsevier]

Tb3+/Eu2+,3+-doped zinc aluminoborosilicate glasses were prepared using a conventional high temperature melt-quenching method. Infrared spectra and physical properties of as-prepared glasses verified that the addition of Tb/Eu causes structural weakness in the glass. Tuning of blue, green, and red emission bands achieves white light for the zinc aluminoborosilicate glasses. The broad blue emission band is attributed to the 5d-4f transition of Eu2+ due to partial reduction of Eu3+ during calcination in ambient atmosphere. The reduction of Eu3+ is related to the formation of Eu Zn • and V Zn '' defects and host alkalinity decreases with the addition of Eu3+. Emission spectra and decay curves confirm energy transfer from Tb3+ to Eu3+ in the zinc aluminoborosilicate glasses, and relative intensities of green and red luminescence can be tuned through concentrations changes of Tb3+ and Eu2+,3+. When the concentrations of Tb3+ and Eu2+,3+ are equal to 6% and 1.2%, respectively, a neutral white light emitting glass is obtained. Furthermore, the white-emitting glass shows very high thermal stability compared to a commercial Y 3 Al 5 O 12 :Ce3+ phosphor. Therefore, luminescence tuning of glasses through changing activator concentrations and energy transfer is expected to achieve high-powered white LEDs. [ABSTRACT FROM AUTHOR]

Cationic substitution is a prevalent strategy to tune the luminescence spectra of phosphors. In this work, we reported a series of Eu2+-activated whitlockite type Ca 7 Sr 3.5-0.5 x A x (PO 4) 7 (CSPA; A =Li, Na, K) (x = 0–1.00) phosphors. The substitution by Na+ for both half occupied/vacant M(4) site was verified via Raman spectra, Reitveld refinement and HR-TEM, whereas a similar accommodation of K+ into the Ca 2 Sr(PO 4) 2 (CSP) host cannot be realized due to the significant size mismatch. A continuous increase of Na+ contents led to the progressively structural contraction, promoting the migration of Eu2+ activator from looser M(4) to other sites, and regulating the luminescence behaviors. Consequently, the gradual red-shift of emission band terminated at a new yellow phosphor Ca 7 Sr 3 Na(PO 4) 7 :0.04Eu2+. The cation vacancy repair developed in this work can not only migrate the Eu2+ activator among different cation sites, but also serves as a new strategy for tuning the luminescence properties of phosphor. [ABSTRACT FROM AUTHOR]

Ce 3+ single-doped Ca 3 (SiO 3 ) 3 phosphors were synthesized by a traditional solid-state reaction at elevated temperature. The phase impurities of phosphors prepared at different conditions were characterized and analyzed and an optimal one was obtained. The synthesis and luminescent properties of the phosphors were studied in detail. As a result, two different emission bands can be observed under excitations at 330 and 360 nm, which peak at 380 and ∼400 nm, respectively. Further analyses of emission spectra reveal that there should exist four different emission bands originating from four Ce 3+ luminescence centers on different Ca 2+ sites. The phosphor with optimal Ce 3+ content [Ca 2.82 (SiO 3 ) 3 :0.18Ce 3+ ] exhibits high absolute quantum efficiencies up to 90.1% and 79.5% for emission bands at 380 and 400 nm, respectively. Moreover, the emission intensity of Ca 2.82 (SiO 3 ) 3 :0.18Ce 3+ at 150 °C remains ∼65% of that at room temperature. The phosphor deserves further investigation for the purpose of application in pc-WLEDs. [ABSTRACT FROM AUTHOR]

CaAl 12 O 19 : Mn 4+ has been reported as a red phosphor with good color purity. A quaternary-doping strategy was adopted to improve the optical properties in this work. Phosphors of general formula Ca 1- m Al 12- x-y-n O 19 : x Mn 4+ , y Mg 2+ , m Bi 3+ , n B 3+ (CAO:MMBB) were synthesized by high-temperature solid-state method. A broad band deep-red emission from Mn 4+ centered at 654 nm was observed, and two strong absorption bands within the ultraviolet range (350–400 nm) and blue-green region peaked at 460 nm were confirmed. The incorporation of co-dopants brought about a remarkable enhancement of the luminescence intensity. The quantum yield of CAO:MMBB reached 84.9%, which is approximately 1.35 times higher than that of as-reported binary-doping phosphors CaAl 12- x-y O 19 : x Mn 4+ , y Mg 2+ (CAO:MM). The possible mechanism of co-doping Bi 3+ and B 3+ ions was discussed in detailed. CAO:MMBB phosphor shows a dual application in agriculture either as solar spectral conversion auxiliary in greenhouse plastic films or as a red component in blue-chip based plant growth light emitting diodes (PG-LEDs). [ABSTRACT FROM AUTHOR]

Photoconversion Tb 0.7 La 0.3 ZnAl 11 O 19 :Cr3+ phosphors possess high efficient ultraviolet/green-excitation and far-red emission performance. It can be assembled into pc-LED plant growth light, which modulated the optimal action spectrum for indoor plant growth. Also, it can be made into luminescent film laminated glass (LFLG) adjusted the composition of the solar spectrum for greenhouse plant growth. [Display omitted] • Tb 0.7 La 0.3 ZnAl 11 O 19 :Cr3+ (TLZA:Cr3+) phosphor possess NUV and green to far-red conversion properties. • Energy transfer efficiency from host to dopant in TLZA:6%Cr3+ phosphor reached 99.62 %. • The IQY of TLZA:6%Cr3+ phosphor reaches over 70 % under NUV or green light excitation. • TLZA:Cr3+ assembled pc-LED could modulate the optimal action spectrum for indoor plant growth. • TLZA:Cr3+ coated LFLG adjusted solar spectrum to promoted plant growth in greenhouse. Phosphor-converted materials have recently become promising candidates for the next generation horticulture and agriculture owing to their ability to overcome the daily sunlight limitations. Here, Tb 0.7 La 0.3 ZnAl 11 O 19 :Cr3+ (TLZA:Cr3+) was prepared by a high-temperature solid state method, which showed high near-ultraviolet (NUV) and green light to far-red conversion efficiencies. In the optimized TLZA:6%Cr3+ phosphor, the energy transfer from the host to the dopant was carried out through a dipole-quadrupole interaction mechanism with an efficiency of 99.62 %. The phosphor-converted light-emitting diode (pc-LED) devices were fabricated by combining TLZA:6%Cr3+, blue and red phosphors with 380 nm NUV-chips, which modulated the optimum action spectrum for indoor plant growth. TLZA:6%Cr3+ luminescent film laminated glass (LFLG) adjusted the composition of the solar spectrum to red/blue light ratio of 3:1 and promoted plant growth in outdoor horticultural greenhouses. Therefore, the pc-LED and LFLG fabricated with the TLZA:6%Cr3+ phosphor in this work are excellent spectral control devices for indoor plant lighting and outdoor horticultural facilities, respectively. [ABSTRACT FROM AUTHOR]

A range of Ca 10.5-1.5 x La x (PO 4 ) 7 :Eu 2+ phosphors were synthesized by high temperature solid state method. Subsequently we studied the crystal structures and luminescent properties through X-ray diffraction, photoluminescence and photoluminescence excitation, diffuse reflection spectra, Raman spectra and decay curves systematically. Based on the special crystal structure of β -Ca 3 (PO 4 ) 2 :Eu 2+ , its emission undergoes a variation from violet–blue to cyan through introducing La 3+ . The substitution of La 3+ for Ca 2+ could form some cation vacancies in Ca(4) sites according to the scheme 3Ca 2+ = 2La 3+ + □ due to the different ion valence, which compels Eu 2+ to migrate from Ca(4) site to other sites. Additionally, the formation of the cation vacancies can further reduce the thermal stability of phosphors. [ABSTRACT FROM AUTHOR]

High quantum efficiency is a vital parameter of phosphors for practical application. An efficient near-UV and blue emitting phosphor Li 4 SrCa(SiO 4 ) 2 :Ce 3+ was synthesized by a traditional solid-state reaction, and luminescent properties were studied in detail. The Ce 3+ -activated phosphor can emit both a near-UV light centred at 345 nm and a blue light peaking at 420 nm when Ce 3+ occupies the Sr and Ca site, respectively. The internal quantum efficiency (IQE) of Li 4 SrCa(SiO 4 ) 2 :0.03Ce 3+ is as high as 97% under the excitation at 288 nm, while the external quantum efficiency (EQE) is 66%. The IQE and EQE values of Li 4 SrCa(SiO 4 ) 2 :0.03Ce 3+ under the excitation at 360 nm are 82% and 31%, respectively. [ABSTRACT FROM AUTHOR]

• The Ca 1.1 Sr 0.9 SiO 4 crystal structure possess the highest rigidity in the series Ca 1- y Sr y SiO 4. • The synergistic effect of the Si4+ substitution by Al3+ and the halide flux addition can finely tuned the ultraviolet to blue (VTB) luminescent properties of Ca 1.1 Sr 0.9 SiO 4 :Ce3+,Li+ phosphor. • Highly efficient VTB phosphor can precisely control solar spectral conversion for enhancing photosynthesis and increasing crop yield and nutritional quality. • The established VTB fingerprint is helpful for efficient cultivation of different crops. A series of Ce3+-doped Ca 1.1 Sr 0.9 SiO 4 -based phosphors has led to the development of a fingerprint spectrum to precisely tune the UV to blue light conversion for application in the photosynthesis of different plants in agriculture. The addition of MX 2 flux (M = Ca, Ba; X = Cl, Br) not only remarkably enhances the luminescence efficiency, but also fine tunes the photoluminescence (PL) wavelength and photoluminescent excitation (PLE) peaks. With increasing Al content doping in the Si site, the excitation and emission peaks of the Ca 1.08 Sr 0.88 Si 1- z Al z O 4 :0.02Ce3+,0.02Li+,0.04CaCl 2 (CSSA:CeLiCaCl) phosphor shift to longer wavelengths, i.e. from 367 (z = 0) to 373 (z = 0.04) nm and from 429 (z = 0) to 448 (z = 0.04) nm, respectively, along with an increase of the luminescence intensity. Rietveld refinement of the XRD data for Ca 2- y Sr y SiO 4 (y = 0.8, 0.9, 1.0) revealed that Ca 1.1 Sr 0.9 SiO 4 has the highest rigidity, which can be correlated with the shortest Si-O bond length and strongest bond energy along the series. The crystal structure and unit cell parameters of CSSA:CeLiCaCl (z = 0, 0.03 and 0.05) were also obtained, revealing that the efficient and tunable blue emission of the CSSA:CeLiCaCl phosphors can be attributed to the crystal structure distortions induced by the [(Si/ Al)O 4 ] tetrahedron, while high rigidity is maintained. The combined effects of the Si4+ substitution by Al3+ and flux addition on the crystal structure and luminescence properties of the Ce3+-doped Ca 1.1 Sr 0.9 SiO 4 phosphors are discussed in detail. Graphical abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Eu2+ and Mn2+ coactivated β- Ca3( PO4)2 ( TCP) phosphors have been prepared by high-temperature solid-state reaction. The site occupation and photoluminescence properties of Eu2+ and Mn2+ have been identified and discussed in detail. The energy transfer from Eu2+ to Mn2+ in TCP: Eu2+, Mn2+ phosphors has been validated and demonstrated to be a resonant type via a dipole-quadrupole mechanism, and the critical distance ( R C) calculated by concentration quenching method is 21.76 Å. A color-tunable emission from violet-blue to red in TCP: Eu2+, Mn2+ phosphors can be realized via the energy transfer from Eu2+ to Mn2+ ions. [ABSTRACT FROM AUTHOR]

Abstract: Eu2+-doped Li4SrCa(SiO4)2 phosphor was synthesized by a high temperature solid-state reaction. There are two different crystallographic sites, namely, a Sr2+ site and a Ca2+ site in the cell of Li4SrCa(SiO4)2, which can be occupied by Eu2+ ions and will generate two emission bands. However, three different emission bands were observed in this phosphor. The first one is peaking at 433nm with the corresponding excitation band at 250–400nm. The second one is at 584nm under the excitation at 395nm, which shows lower emission intensity than that of the blue emission. The third one is at around 615nm under the excitation at 460nm. Analysis suggests that the 433nm emission belongs to Eu2+ on Sr2+ site, and the 584nm emission originates from Eu2+ on isolated Ca2+ site. The 615nm emission may be related to Eu2+ clusters. [Copyright &y& Elsevier]

[Display omitted] • Nominal K m-0.4 Al 11 O 17+δ :0.2Eu2+ (beta-alumina phase) has (KEu)/Al higher than 1:11. • Phosphors exhibit high quantum efficiency (QE) and thermal stability. • Internal QE of nominal K 1.6 Al 11 O 17+δ :0.2Eu2+ is 97.1%, and external QE is 61.8%. • The phosphor exhibits zero-thermal-quenching behavior within 150 °C. • White phosphor-converted LEDs show high CRI values pumped by n-UV or violet chip. Discovery of highly efficient and thermal stable phosphors is a major topic in phosphor-converted white light-emitting diodes (LEDs). A highly efficient and zero-thermal quenching blue-emitting phosphor is realized in nominal K m -0.4 Al 11 O 17+δ :0.2Eu2+, which benefits from rigid aluminate structure with space group P6 3 /mmc and the introduction of trap energy levels. The internal and external quantum efficiencies of optimal nominal K 1.6 Al 11 O 17+δ :0.2Eu2+ are 97.1% and 61.8%, respectively. The phosphor exhibits zero-thermal-quenching behavior within 150 °C. Further increasing K content results in even better thermal stability, however, lower quantum efficiency. The relationship between luminescence properties and crystal structure was discussed. Results suggest that the blue-emitting phosphor is a candidate for white phosphor-converted LEDs based on near-UV or violet chip. [ABSTRACT FROM AUTHOR]

A single-phase multicolor emitting phosphor, Ca3Al2O6:Ce3+,Li+, was prepared by a solid-state reaction. When the Ce3+ concentration is lower than 0.030 (molar ratio in Ca3Al2O6), yellow and greenish blue emissions can be observed under the excitation by a blue and a near UV light, respectively. The yellow-emitting phosphor possesses an internal quantum efficiency of 89%. Additional purplish blue emission turns up when Ce3+ concentrations are higher than 0.040. Tunable emission bands are originated from Ce3+ ions on different Ca sites in Ca3Al2O6. Although the emission band of purplish blue or greenish blue overlaps the excitation band of yellow emission, and the distances between the unlike Ce3+ ions are in the range of electric dipole-dipole interaction, no energy transfer is observed. Furthermore, emission wavelengths for the yellow, greenish blue, and purplish blue emission show little change upon increasing Ce3+ concentrations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pure-phase phosphor CaZnOS:Eu2+ was synthesized by co-doping with Ce3+ as deoxidizer. [•] Energy transfer mechanism from Ce3+ to Eu2+ in CaZnOS host is proposed. [•] CaZnOS:Eu2+, Ce3+ phosphor has good chemical and thermal stability performance. [•] The similarities and differences between CaZnOS:Eu2+ and CaS:Eu2+ were analyzed. [•] The green excitation and red emission show superior solar harvesting for plants. [ABSTRACT FROM AUTHOR]

Thermal stability and quantum efficiency are crucial parameters for phosphors when they act as components in phosphor-converted white light-emitting diodes (pc-wLEDs). Therefore, it is important to explore phosphors with highly thermal stability and quantum efficiency. Blue-emitting Ce3+-activated (Ba 1- x Sr x) 3 Y 2 (BO 3) 4 phosphors were synthesized through high-temperature solid-state reaction. X-ray powder diffraction suggests the success of complete solid solution in the phosphor series. Scanning electron microscope (SEM) image and elemental mapping suggest uniform distribution of Ba and Sr atoms in the phosphor particles. Rietveld refinement indicates that cell volume decreases with increasing the content of Sr2+, while the related emission peak exhibits a slight blue shift, which implies the existence of remote control effect. Both thermal stability and quantum efficiency increase with the evolution of solid solution from Ba 3 Y 2 (BO 3) 4 :Ce3+ to Sr 3 Y 2 (BO 3) 4 :Ce3+, which is due to the increase of structural rigidity. The emission intensity of Sr 3 Y 1.94 (BO 3) 4 :0.06Ce3+ at 423 K remains ∼56% of the room-temperature value. The internal and external quantum efficiencies of Sr 3 Y 1.94 (BO 3) 4 :0.06Ce3+ are ∼93% and ∼67%, respectively. A pc-wLED was fabricated with a 365 nm UV chip, Sr 3 Y 1.94 (BO 3) 4 :0.06Ce3+, commercial green phosphor, and commercial red phosphor, which exhibits a color rendering index of 94.5. This work provides an example on the adjustment of luminescent properties through solid solution. Image 1 • Ce3+-activated (Ba 1- x Sr x) 3 Y 2 (BO 3) 4 solid solution phosphors were synthesized. • Cell volume decreases while structural rigidity increases upon increasing x. • Emission exhibits slight blue shift upon increasing x due to remote control effect. • Quantum efficiency and thermal stability both increase with structural rigidity. [ABSTRACT FROM AUTHOR]

Abstract: A Eu2+ doped LiSrBO3 phosphor has been synthesized by a double-sintering process under a reducing atmosphere on the purpose of searching broad-band red phosphors. LiSrBO3: Eu2+ shows a broad emission band with a maximum at 618nm under excitation of 460nm-light, which is due to a large covalency and a high crystal field splitting. Although a phosphor-converted LED was fabricated with the synthesized LiSrBO3: Eu2+ and a 460nm-emitting InGaN chip, this phosphor cannot be applied in LED until the quantum efficiency is improved. [Copyright &y& Elsevier]

• Phase segregation occurs during the high-temperature synthesis of inorganic phosphor. • EuBO 3 segregated and accompanied by transformation from Na 2 Al 2 B 2 O 7 to NaAl 11 O 17 :Eu2+. • More rigid structure for NaAl 11 O 17 allows dramatical enhancement of blue emission. • NaAl 11 O 17 :Eu2+ remains 96% of the room-temperature emission intensity at 150 °C. Thermally stable phosphors are crucial for the application in phosphor-converted white light-emitting diodes. This paper reports the evolution of phase compositions in nominal Na 2− x Al 2 B 2 O 7 : x Eu (x = 0.02–2.0) upon replacing Na atoms by Eu atoms. Eu2+-activated blue-emitting phosphor was discovered through phase segregation combined with related analyses. The structure, phase composition and related luminescent properties were investigated by X-ray powder diffraction, backscattered electron image combined with elemental mapping, cathodoluminescence-combined scanning electron microscope, and temperature-dependent emission spectra, etc. Analyses results suggest that EuBO 3 phase segregates upon the gradual replacement of Na by Eu atoms, which is accompanied by phase transformation from Na 2 Al 2 B 2 O 7 :Eu2+ to NaAl 11 O 17 :Eu2+ and dramatic enhancement of blue emission. The broad emission band is peaking at around 470 nm under UV irradiation. The internal quantum efficiencies of nominal Na 0.4 Al 2 B 2 O 7 :1.6Eu and Na 0.2 Al 2 B 2 O 7 :1.8Eu are 58.6% and 60.2%, respectively, which contain both NaAl 11 O 17 and EuBO 3 phase. The emission intensity for these two samples at 150 °C remains 96% (x = 1.6) and 83% (x = 1.8) of the room-temperature values, respectively. [ABSTRACT FROM AUTHOR]

Li4SrCa(SiO4)2:Ce3+ is prepared by calcination of stoichiometric amounts of Li2CO3, SrCO3, CaCO3, SiO2, and CeO2 in 5% H2/N2 (800-1100 °C, 4 h). [ABSTRACT FROM AUTHOR]